Streetability mods

fdicrasto · Post by **fdicrasto** » Sat Apr 20, 2019 2:04 pm

So a customer of mine from 2011 called wanting to run straight pump gas in his 67 dart. Engine is 340-360 stroked to 415. Scat rotating assy. with 71-72 "J" heads, 2.02" int and 1.6" ex. I ported these heads fully but conservatively, incorporated a Lunati Voodoo hyd.roller 231/239 @ .050 , Edelbrock air gap rpm manifold, 750 d.p. out of box carb, 1 5/8-1 3/4" step headers with actual C.R. 11 to 1. Peak torque at 4200 was 567 lb-ft. Peak hp @5600 was 512 hp. this was with 35 degrees total timing and VP 112. I explained that it will definitely cost him some power but he has tired of mixing pump gas w/ VP. We did try pump on dyno with timing back but it started rattling so aborted that. What do you guys feel would be the least complicated way to accomplish this. I've retired to Florida and he is in upstate NY so he is on his own sorta.

F-BIRD'88 · Post by **F-BIRD'88** » Sat Apr 20, 2019 2:15 pm

Exactly which "Straight pump gas" is he going to buy and fill the tank with? 87 octane.... 91 octane,, 92.,93,94.
Be specific. ,ya it matters. True 10:1 is a good place to be with 92 octane unleaded premium.

The best way to reduce the cr depends on the build.
On a stroked LA (415) probabily change pistons.
If he wants it to run on 87 reg gas drop the cr to 8.8- 9:1
Thats the best you will do with the oem cast iron heads.

Some (but not all) of the Delta Sonic car wash/gas bars in Upstate NY sell real deal 100 octane unleaded at the pump.
Sold as
"Sunoco GT100 or " CAM2” Until he is prepared to make mechanical engine chsnges to lower the compression ratio for pump gas this is a alternative. Have a look.
Yup mixing race gas for the street gets old, quick.

randy331 · Post by **randy331** » Sat Apr 20, 2019 2:18 pm

If 100LL av gas is close by he could run that straight. At 11-1 it be nothing for av gas to handle. Here it's $4.05 a gallon. 91 is $3 here and it'd still need less compression to run it.

Av gas is way better fuel than anything considered pump gas.

Otherwise, it's pull the engine apart.

Randy

fdicrasto · Post by **fdicrasto** » Sat Apr 20, 2019 2:27 pm

The best unleaded pump gas he has available is 92. He did say he wouldn’t mind putting a bottle of octane boost if that will cover his need. Presently has .038” felpro head gaskets so there are various other options there. He doesn’t want to pull heads if possible.

fdicrasto · Post by **fdicrasto** » Sat Apr 20, 2019 2:33 pm

I will definitely have him check on av gas availability and the Delta Sonic possibility also. Thanks for that info guys.

F-BIRD'88 · Post by **F-BIRD'88** » Sat Apr 20, 2019 2:34 pm

The lil bottles of Octane booster will cost more than blending in race gas costs. For 92 octane premimun get the true measured cr to 9.80:1 10:1 max.
There is no magic. Heads and more will be coming off.
10:1 will not slow this car down. Real changes are required.
He can do it now while this engine is still healthy or do it all over again when detonation ruins this engine.
Are there D dish pistons available for this stroker engine?
Forget the lil cans of octane booster.

Wolf_Tm250 · Post by **Wolf_Tm250** » Sat Apr 20, 2019 3:25 pm

What about installing a water (or water/meth) injection system?
This will decrease the tendency to knock, as it was an higher octane rating fuel

Post by **jcisworthy** » Sat Apr 20, 2019 3:27 pm

Some areas in upstate have E85 which could be an option

F-BIRD'88 · Post by **F-BIRD'88** » Sat Apr 20, 2019 3:45 pm

Water/meth injection is possible but on a N/A engine with excessive high compression the amount of W/M needed is always a moving target. Where as say a roots supercharged application there is always a source of excess heat that needs to be consumed.
A N/A type water injection system is a complicated sub fueling system that needs constant changing flow regulation with 3D electronic control same as Modern EFI and also needs maintanance. It is harder technically than mixing gasoline and you have to stay on top of it. There is always this added cost of operation. And it is always there. It is much like NOS... You are always paying rent instead of owning the power.

Replacing the pistons now is a real fix that you only have to do once.
Building a carbed street motor with 11:1 cr is a big mistake and there is no free lunch. Nor cheap fix on this. 11:1 on this type of carbed street motor needs 98 to 102 octane gas. There are many good engine shops in Western NY that can correct the excessive compression ratio fault for this person. This the real fix.

Both conversion and ongoibg use of both/either E85 or added W/M injection will be near the cost of replacing the pistons now and will soon over a short time end up costing much more. It is never paid for on a street engine. Excessive compression ratio for the fuel is probabily the biggest mistake made by owners and by engine builders (even pros) of high perf street cars.

Kenova · Post by **Kenova** » Sat Apr 20, 2019 3:54 pm

Newer aluminum heads with bigger combustion chambers.
Not exactly cheap, but it may be the easiest route.

Ken

F-BIRD'88 · Post by **F-BIRD'88** » Sat Apr 20, 2019 3:56 pm

Research to see if there is a similar piston with a deep dish enough to drop the cr to 10:1.. That is same weight.
The pin weight can be played with a bit. The pin bosses can be played with on a close piston. Start there.
A D dish is best. Keeps the effective quench action.

Wolf_Tm250 · Post by **Wolf_Tm250** » Sat Apr 20, 2019 3:58 pm

F-BIRD'88 wrote: ↑Sat Apr 20, 2019 3:45 pm Water/meth injection is possible but on a N/A engine with excessive high compression the amount of W/M needed is always a moving target.

It will just need a simple 3D mapping as if it was a fuel map.
Nothing that's impossible to do with modern Water Injection Systems:
http://www.aquamist-direct.com/806-063- ... pwm-valve/

F-BIRD'88 · Post by **F-BIRD'88** » Sat Apr 20, 2019 4:06 pm

Wolf_Tm250 wrote: ↑Sat Apr 20, 2019 3:58 pm
F-BIRD'88 wrote: ↑Sat Apr 20, 2019 3:45 pm Water/meth injection is possible but on a N/A engine with excessive high compression the amount of W/M needed is always a moving target.
It will just need a simple 3D mapping as if it was a fuel map.
Nothing that's impossible to do with modern Water Injection Systems:
http://www.aquamist-direct.com/806-063- ... pwm-valve/

The cost exceeds the cost of new pistons.
W/M overtime is just not a practical solution on a turn the key and go N/A street car. It is much more practical and simpler if on a supercharged street car.
On a N/A street car (that gets driven more than a very limited amount) its at best a temperary short use limited use , patch fix. Its fun but gets old quick just like mixing race gas does.

F-BIRD'88 · Post by **F-BIRD'88** » Sat Apr 20, 2019 4:13 pm

If on the engine if the CR is 11:1 now and the combustion chamber is 64cc and the piston is flat top with say 7cc valve reliefs then look for a dished piston with a 22 cc Dish volume. The cr will be 10:1. Again a D dish is best.
Need exact engine specs to get the exact needed dish volume....

F-BIRD'88 · Post by **F-BIRD'88** » Sat Apr 20, 2019 4:28 pm

New aftermarket Chrysler LA cylinder heads cost a lot more than new pistons do. New correct pistons are not cheap but new heads are not cheaper.
But could be a good buy and a good fix.
Plan on 10:1 cr 10.5:1 real MAX on this with aluminum heads. Look for a aluminum head with a 76 to 78 cc combustion chamber to fix this.
If the piston is 7cc flat top now.

Don Terrill’s Speed-Talk

Streetability mods

Streetability mods

Re: Streetability mods

Re: Streetability mods

Re: Streetability mods

Re: Streetability mods

Re: Streetability mods

Re: Streetability mods

Re: Streetability mods

Re: Streetability mods

Re: Streetability mods

Re: Streetability mods

Re: Streetability mods

Re: Streetability mods

Re: Streetability mods

Re: Streetability mods